The invention relates to a variable capacitance diode comprising a low resistance semiconductor substrate and an epitaxial layer arranged thereon with an impurity concentration which decreases towards the semi-conductor substrate and with a barrier layer arranged in or on the epitaxial layer and opposite the semiconductor substrate.
Variable capacitance diodes are used to tune the frequency of resonant circuits for the UHF range for example. They are intended to have a low series resistance and a fixed C(U) characteristic and produce a constant tuning amplitude in the resonant circuit. The curve of capacitance over the applied D.C. voltage and the series resistance of the variable capacitance diode depend to a large extend on the doping profile in that part of the diode in which the space charge region extends when voltage is applied, this voltage being across the barrier layer in the reverse direction.